In the field of bicycle training and racing, a number of objective and subjective criteria may be used to judge to level and quality of a cyclist's performance in a particular event or training activity. These criteria may be used to determine or estimate the cyclist's overall ability or training level as well as the cyclist's ability with regard to specific aspects or types of exertion. These criteria may also be used to determine the degree to which that overall ability or specific aspects of ability were utilized in the event or training session. This information can then be used to tailor specific approaches to future events or training activities.
Since some of the criteria that may be used are subjective and may fluctuate based on a variety of factors that may or may not be apparent, it has become increasingly desirable, among cyclists, to focus on one or more objective performance measurements. One of these objective standards used may be the mechanical power generated by the cyclist that enables the bicycle to move forward. The speed at which the bicycle moves is dependent on a wide array of environmental factors and equipment characteristics. Thus, measuring the response to the power generated by the cyclist may not be representative of physical workload, as all of the external factors should be accounted for in some fashion.
By measuring the power generated directly, rather than the reaction to the power generated, a more objective measure of the level of effort exerted by the cyclist may be determined fairly quickly and easily.
Conventional power meters measure power in three primary ways: at the crankset, in the chain being moved by the crankset, or at the hub being driven by the chain. Measurements relying on the chain have been conventionally indirect and have generally been the least precise and accurate. Measurement at the driven hub can be quite accurate but the power measured represents the power generated by the cyclist minus any drive line losses that occur in the transmission of the power to the hub. In some cases, these losses may be significant and are dependent on a number of external factors, such as the length and quality of the chain, bearing losses, flexibility of the bicycle or components of the drive line, and other variables. These variables may change over time or based on the power being generated and transmitted. Thus, measuring power at the driven hub must also deal with external factors that may be unknown or too variable to accurately account for.
Conventional crankset power measurement systems but may include some inherent inaccuracies or operational issues that will be described below. Improvements to bicycle power measuring systems are desirable.